Of rotary pivoted vane pumps two principal types are known. In one type the vanes are disc-form and are rotatable about pivot axes which are radial to the axis of rotation of the rotor. In the transport channel portion the vanes are perpendicular to their direction of movement while in the sealing portion of the channel they are parallel to the direction of movement. Because of their disc form, the cross sectional area of the blades in a plane containing the axis of rotation of the rotor is greater in the transport portion of the channel than in the sealing portion. The pivoted vanes are frequently formed as flat circular discs. Pumps of this kind are described for example in U.S. Pat. Nos. 3,895,893 and 3,985,479.
In another type of pivoted vane rotary pumps the pivot axes of the vanes are parallel rather than radial to the axis of rotation of the rotor. In many pumps of this kind the vanes are retracted into recesses in the hub so that their cross sectional area in a plane containing the axis of rotation is zero in the sealing portion of the channel. Radial pivoted vane pumps of this kind are described for example in German patent specification No. 28 45 658. In order to cause the vanes to pivot, the transport channel is frequently formed so that it is restricted at one side of the pivot axis so that the vanes are caused to pivot by the restriction. The return movement of the vanes is effected either by springs or by coupling a vane with a vane at the opposite side of the axis of rotation so that pivoting of one vane by the narrowing of the transport channel will cause the opposing vane to pivot to open position.
Pivoted vane rotary pumps have particularly desirable pumping characteristics for certain applications. For example they are superior to other pumps for pumping abrasive materials such as chrom (III) oxide sludge or for pumping delicate food-stuff such for example as whole fruit in a syrup, soup containing solid pieces or salads.
In pumping foodstuffs there is not only the problem that they must be carefully handled but also the further problem that the hygienic condition of the pump must be carefully maintained and also that pump parts must not be attacked through corrosive media such for example as fruit acids or vinegar. In order to avoid such attack of the pump parts, pumps for use in the sanitary field have heretofore been produced of stainless steel.
For pumping highly abrasive material, pivoted vane rotary pumps have heretofore used an expensive pivoted vane construction in which the vanes have a plastic covered metal core with special sealing attachment.
In accordance with the present invention there is provided a pivoted vane rotary pump which is of simple construction and easily produced and with which on the one hand food-stuffs can be gently and hygienically pumped while on the other hand abrasive media can be pumped in an abrasion resistant manner.